Heretofore, in four barrel multistage carburetors, a linkage has connected the secondary throttles to the primary throttles with the secondary throttles being opened upon rotation of the primary throttles and in wide open throttle position simulataneously. The linkage heretofore has been disconnected until the choke valves have been opened at which time the linkage has been connected for opening of the secondary stage. When the engine has been cold the linkage has been disconnected and thus the secondary throttles are prevented from opening.
However, with the addition of pollution control devices on internal combustion engines for optimum exhaust emissions, the choke valve is opened early and oftentimes before the engine has reached its normal or optimum operating temperature. When this occurs, the secondary throttles can be opened prematurely which results in a heavy engine load before the engine has reached its normal operating temperature. This could possibly cause engine malfunction and effect engine life.
An example of a multistage carburetor in which a linkage has been provided between the primary and secondary throttles and responsive to the opening of the choke valve is illustrated in U. S. Pat. No. 3,575,385, dated Apr. 20, 1971. The movement of the choke valve to full open position moves the latch to a latched position thereby to connect the linkage between the primary and secondary throttle valves for rotation of the secondary throttle valves to an open position.